This relates to apparatus, systems and methods associated with electronically driving actuator apparatus including radio frequency switches.
Arrays of radio frequency (“RF”) switches are used in the fields of communication, test and instrumentation, and RF microphones, among others. Such RF switch arrays are increasingly implemented using RF micro-electromechanical (“MEMS”) devices. RF MEMS devices in this context may include MEMS arrays of tunable inductors, switched capacitors, and varactors in addition to simple switches. RF switching arrays implemented with RF MEMS devices include the advantages of compact size and low power dissipation. Although the switching element input voltage for such devices is relatively high for semiconductor devices (e.g., typically 30-40 volts DC), each MEMS element requires only a small or near-zero drive current to maintain its state following a state transition.
The design of electronic drivers for the above-described RF switch arrays can present challenges. RF energy from driven devices may conduct back from an RF switching element in the array to the driver for that element. The RF energy may generate inter-modulation products through mixing within the driver transistors. The inter-modulation products may reflect back out into the RF channel. Conversely, spurious noise from driver elements may leak into the RF switch array. The latter driver-initiated interference is referred to hereinafter as “spurious noise.” Spurious noise may include, for example, noise from a power supply providing the high drive voltage to bias the RF switch elements.
Spurious noise leakage may cause subtle but significant variations in sensitive parameters such as the capacitance of a MEMS varactor element or result in inter-modulation distortion by mixing the baseband with the RF band carrier.